austic soda ( Insoluble metal hydroxides, hydroxide), often formed by reaction of caustic referred to as caustic soda with wastewater metals, or lye, is the principal are removed physically as part of Cproduct that accompanies the wastewater pre-treatment chlorine production. (For more process. details on chlorine, please see Caustic soda also may be used to the insert Chlorine Chemistry’s neutralize acid mine drainage. Role in our Daily Lives.) When air and water contact newly exposed sulphur- Caustic soda is co-generated with chlorine by electrolysis of containing minerals during mining operations, the minerals brine using one of three rapidly oxidize, releasing damaging quantities most common industrial manufacturing Caustic Soda of acidity, metals and other chemical technologies. (For more details, please see End Uses components to the environment. Acid mine the insert Chlor-Alkali Manufacturing drainage is a major environmental hazard. Processes.) In the electrolysis process, it is Caustic soda is particularly effective for simultaneously produced in a fixed ratio neutralizing low flows of acid mine drainage of 1 tonne of chlorine and 1.12 tonnes of in remote locations and for treating flows caustic. In 1998, worldwide production having high manganese content. capacity of caustic soda was approximately 54 million metric tonnes. Organics 18% Helping keep us clean Pulp & paper 16% Caustic soda is used in a wide variety of Caustic soda plays a significant role in the Inorganics 15% industrial applications. It is valued for its Soap & detergents, 10% manufacture of powder soaps, bar soaps and neutralizing power and is used to control textiles detergents, with a considerable amount being and remediate acidic environmental Alumina 8% used in the production of industrial and pollution. As such, it is used in many Water treatment 5% specialty soaps. Developing countries have a processes for acid control, neutralization Other 28% high demand for caustic soda since, in some of waste acids and gas scrubbing. countries, bar soaps are used almost exclusively to wash clothes and for personal hygiene. In addition, like chlorine, it is used as an intermediate to Specialty soaps include oven and food preparation produce numerous other products, such as sodium equipment cleaners, heavy-duty dishwashing detergents, phenolate used in antiseptics and in producing aspirin and industrial floor cleaners, metal amyl alcohol used in the production of pharmaceuticals. cleaners, paint strippers (Please see inside for a detailed look at the end products.) and many other applications. Helping in pollution control Numerous diverse uses Because caustic soda is an alkaline compound, it is the Caustic soda is used in the chemical opposite of acids and is capable of neutralizing production of cotton fabrics them. The neutralization reaction produces water and . to help improve fibre strength Caustic scrubbers are air pollution control devices designed and absorption of dyes. It is to make use of the alkaline properties of caustic soda. These estimated that about 90 systems neutralize acid gas stack emissions, thus helping to percent of cotton is treated contribute to a cleaner environment. using caustic soda. It also has a variety of uses in the food In addition, metal plating facilities, for example, produce industry, to refine animal and vegetable oils to remove wastewater containing concentrations of dissolved heavy fatty acids and to peel potatoes, fruits and vegetables. In metals that must be removed addition, it is used in the prior to wastewater release to production of pulp and paper municipal sewers or receiving and aluminium. Significant waters. This is typically amounts of caustic soda are also accomplished by adding an used for industrial and alkaline chemical, such as municipal water treatment. caustic soda, to the wastewater.

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April 2002 Caustic Soda Chemistry and End Product Uses

Catalyst Dyes SODIUM POLYSULFIDE XYLENESULFONIC ACID Synthetic detergents Cosmetics Electroplating SODIUM SULFITE Gelling agent Petroleum additives Grease Sulfur dyes Aluminum stearate Pharmaceuticals Synthetic rubber Plastics stabilizer SODIUM ARSENITE Soaps Textile desizer SODIUM STEARATE Calcium stearate SODIUM BROMITE Zinc stearate Food additive Activator for rubber vulcanization Surface-active agents Fungicide Zinc dimethydithiocarbamate SODIUM DIMETHYL DITHIOCARBAMATE SODIUM LAURYL SULFATE Wetting agent for textiles

Control agent for fruit setting fungicide SODIUM DINITRO-O-CRESYLATE SODIUM NAPHTHENATE Disinfectant Herbicide Driers Emulsifier SODIUM DIURANATE Pollution reduction fuel additive Rodenticide SODIUM TUNGSTATE SODIUM OLEATE Emulsifier Surface-active agents SODIUM FLUOROACETATE TEXTILE PROCESSING Ore flotation Soaps Mercerizing cotton Waterproofing textiles Bleaching agent for molasses and soap SODIUM FORMALDEHYDE SULFOXYLATE Scouring cotton Textile stripping Vat dyeing Adhesives CUPRIC HYDROXIDE Coatings Ceramics Electrical compounds Pigment for fabrics MANGANOUS HYDROXIDE EPOXY RESIN

Batteries (especially for MERCURIC OXIDE Flavors Sodium Sodium miniaturized equipment) Perfumes chloroacetate carboxymethylcellulose Cosmetics Food products Dyes (especially ice cream Paint pigment ABS resins Perfumes ACRYLONITRILE VANILLIN Vitamins and dietetic foods) Automobile body parts as a water binder, thickener, Bristles for toothbrushes, Pharmaceuticals Boats hairbrushes, paint brushes, etc. Polishing compounds 2,4-Dichlorophenoxy- suspending agent and emulsion Business machines NICKEL HYDROXIDE stabilizer Hosiery Electronic equipment housings BERYLLIUM HYDROXIDE GAS SCRUBBING acetic acid Herbicide Paper coatings, prints, Tire cord Luggage Glass manufacture Wearing apparel, alone, Manufacture of oil and grease additives BARIUM HYDROXIDE pharmaceuticals and cosmetics Radiator grills Textile manufacturing (sizing) or in combination with Shoe heels Refining of beet sugar FRUIT & wool and cotton to Shower stalls Steel carbonizing agent VEGETABLE increase wear and crease Telephones Nylon 66 resistance Toys CADMIUM HYDROXIDE PEELING Adiponitrile Hexamethylenediamine Nitrile rubber Cadmium plating COBALT HYDROXIDE Nylon 610 Artificial blood vessels LEAD HYDROXIDE Case hardening and heat treating agent for steel Athletic turf Automotive upholstery Blends with cotton for home furnishings Rayon SODIUM CHEMICALS Cordage and tow lines Fertilizer Ethylenediaminetetraacetic acid (EDTA) Anticoagulant for blood (drapes, bedspeads, tablecloths) Cellulose xanthate Electrical wire insulation Paint pigments and for reducing Fish net and fishing line Coated fabrics Cellophane blood cholesterol Felts and blankets Pharmaceuticals Gears and bearings Liquid soaps Parachutes Nonwoven fabrics Wrapping and SODIUM Shampoos Surgical dressing Pen tips protective packaging MOLYBDATE ETCHING Ore flotation Rugs and carpets Wearing apparel Dyes Flavor enhancer Black nickel plating Sails Adhesives Ethylcellulose Pharmaceuticals Dyeing Surgical sutures ELECTROPLATING Plastics Pharmaceuticals Tennis racket strings Gel lacquers (bowling pins, Adhesives MONOSODIUM electrical equipment coatings) Rubber treatment Asphalt emulsions GLUTAMATE Ink for heat transfer Cements printing on fabric Cosmetics PETROLEUM Extraction agent for gold and silver Lacquers Pharmaceutical lotions REFINING OF KRAFT REFINING production from ores Pharmaceuticals (binder, filler, Electroplating agent for copper, zinc, and jellies Hydroxyethyl (chemical cellulose) (sweetening) protective tablet coating) Textile processing Alkali cellulose brass and cadmium cellulose (HEC) Automotive radiator cleaner ION EXCHANGE Sodium formate Catalyst Coatings and glaze for food items 2-Hydroxypropyl Leather tanning REGENERATION Dye mordant Ink cellulose Mold preventative Purifying agent and intermediate Latex paint Leather tanning agent 2-Hydroxyethyl for food SODIUM PROPIONATE for many chemical compounds Pharmaceuticals Metal plating methyl cellulose (HEMC) Rare earth processing FOOD ADDITIVE Oxalic acid Textile bleaching Antiseptics Pharmaceuticals WOOD PULP Wallpaper printing Appliances Aspirin (acetylsalicylic acid) SODIUM PHENOLATE Automotive trim and instrument panels (soda process) Cosmetics and packaging WALLBOARD Sodium chlorite Bleach for textiles, paper pulp, edible oils, Dinnerware SODIUM METASILICATE GROUNDWOOD and straw products Electrical enclosures Dye intermediate SODIUM ORTHOSILICATE Oxidizing agent for dyes Lawn and garden equipment PULP BLEACHING Medical equipment SODIUM PICRAMATE Toys Wiring devices POLYCARBONATE SODIUM STANNATE Blueprint paper Ceramics and glass ALKALINE BOTTLE WASHING FORMULA Dye mordant Stabilizer for hydrogen peroxide DISINFECTANT HYDRAZINE Blowing agent Textile fireproofing EFFLUENT STREAM TREATMENT Buoyancy agent for undersea salvage Tin electroplating Fuel cells LATEX RUBBER STABILIZERS Pharmaceuticals METAL PROCESSING Caustic Photographic developers Plating metals on glass Ore flotation, Metal degreasing, Aluminum ore (bauxite) Soda Polymerization catalyst pH CONTROL Rocket propellant REFINING VEGETABLE OILS Spandex fibers Source: Charles River Associates (imparts elasticity to garments RUBBER RECLAMATION AGENT such as socks and special hosiery)